The present invention relates to metal working, and more particularly to bending metal conduit, pipe, tubing and the like to a preselected angle.
In various industries, such as the construction and plumbing industries, it is often necessary to bend metal conduit and pipe to a desired angle. Metal conduit and pipe, however, are manufactured in various nominal diameter sizes having various wall thicknesses which are generally referred to as steel and aluminum "rigid" conduit and pipe, IMC conduit and pipe, or "thinwall" (EMT) conduit. These various sizes and types of conduit and pipe have created numerous problems in the design of manual and power driven bending apparatuses. For example, a rigid steel conduit having a 1 inch nominal diameter has an actual outer diameter which is greater than the actual outer diameter of a 1 inch nominal size thinwall conduit. As a result, a plurality of different bending shoes or dies having a hemispherical recess or groove formed therein which matches the size of the conduit and pipe being bent have generally been used in the past in order to provide sufficient support during bending. Shoes having a plurality of different size grooves formed therein have also been used as shown in Hautau, U.S. Pat. No. 3,299,681.
Another type of problem exists when bending larger sizes of thinwall conduit and pipe. The relatively thin wall of this type of conduit and pipe tends to collapse inwardly or kink during bending. Therefore, some means for supporting the inside face of the bend or for cold working the wall of the bend by either stretching or squeezing during bending is needed to prevent collapsing or kinking of the walls. See for example Hautau, U.S. Pat. No. 3,147,792. Other problems well known in the art of bending include providing for easy removal of conduit and pipe after bending, slippage during bending, and springback after bending.
Various power driven bending apparatus have been developed. One such arrangement is shown in Pearson et al, U.S. Pat. No. 3,949,584 wherein there is provided a rotating bending shoe and a roller unit utilizing a pair of rollers acting in tandem for supporting conduit during the bending operation. The rollers shown in the Pearson et al patent, however, may only be utilized with a limited range of conduit diameters and wall thicknesses. As a result, multiple roller units must be utilized to cover the full range of conduit and pipe sizes and types available in the marketplace. Another arrangement is shown in U.S. Pat. No. 4,249,407 in which conduit is bent around a stationary circular die by a rotating member. Other bending machines are shown in U.S. Pat. Nos. 3,417,590 and 1,899,281. Nevertheless, none of the above known bending apparatuses are capable of accommodating the numerous conduit diameters and wall thicknesses available in a single arrangement without the necessity of providing multiple interchangeable bending components for the apparatus.
It is thus desirable to provide a bending apparatus which may accommodate conduit of various diameters and wall thicknesses as well as solve the aforementioned problems.